The use of blow-molded plastic containers has become very commonplace in packaging beverages and other liquid, gel, or granular products. In the packaging of beverages, especially juice, blow-molded plastic PET containers are particularly useful in the so-called "hot-fill" process, i.e. filling the containers with beverages at an elevated temperature, sealing the containers, and then allowing the beverage to cool. Blow-molded plastic containers can have vacuum flex panels which provide sufficient flexure to compensate for the changes of pressure and temperature, while maintaining structural integrity and aesthetic appearance.
Some containers benefit from the use of handles to facilitate a consumer's capability to lift the container and pour its contents either with one or two hands. Smaller sized containers, such as 64 ounces and below, generally do not need handles because a consumer can readily grasp the sides of the container to manipulate the container. However, larger containers, such as gallon containers, may require some form of handle in order for a consumer to control the container while lifting or pouring its contents especially with one hand.
Blow-molded containers having handles have been manufactured using a variety of techniques. For example, handles have been blow-molded integral with the containers. Some containers have separately formed handles which snap into engagement with the neck of the container. Container preforms have been injection molded with handles integral with the neck of the preform. Separately formed plastic handles have been secured to the sidewall of containers by blow-molding the container body around a portion of the handle to capture the handle in place. Separately formed handles have been snap fit into engagement with concavities formed in the sidewalls of fully blow-molded container bodies.
Although various ones of the referenced techniques for producing a blow-molded container having a handle may be satisfactory for their intended purposes, there is a need for a more cost effective and efficient technique for producing blow-molded plastic containers having separately formed, permanently attached handles.
In an effort to meet this need, the assignee of the present application developed hot-fillable, blow-molded containers which are produced by welding a completely separate, injection-molded plastic handle to a fully molded, plastic container. The containers and methods of manufacture are disclosed in pending U.S. patent application Ser. Nos. 08/414,646, 08/694,348 and 08/723,895 which the assignee of the present applications owns. One of the welding techniques disclosed in these applications involves the use of ultrasonic energy to melt the confronting surfaces of the handle and container to produce a weld therebetween.
Ultrasonic energy has been used previously to weld together confronting surfaces of containers and attachments. U.S. Pat. Nos. 4,273,246, 4,280,859, 4,368,826 and 4,372,454 issued to Thompson disclose ultrasonically welding a handle to a container. U.S. Pat. No. 4,293,359 issued to Jakobsen discloses welding a base support cup to the base of a plastic blow-molded container. U.S. Pat. No. 5,275,767 issued to Micciche discloses connecting a base to a sidewall of a container. U.S. Pat. No. 5,256,225 issued to Dwinell; U.S. Pat. No. 5,244,520 issued to Gordon et al.; U.S. Pat. No. 4,726,481 issued to Hagan; U.S. Pat. No. 5,304,265 issued to Keeler; and U.S. Pat. No. 4,746,025 issued to Krautkramer et al. disclose the welding of nozzles, spouts and neck inserts to containers. U.S. Pat. No. 5,040,357 issued to Ingemann; U.S. Pat. No. 4,954,191 issued to Delespaul et al.; and U.S. Pat. No. 5,316,603 issued to Akazawa disclose the welding of lids, covers and seals to containers.
In the course of welding confronting surfaces with ultrasonic energy, so-called "energy directors", or "energy absorbers" are customarily used to provide a strong weld. The energy director is a small raised pattern of plastic which is located between confronting surfaces. The geometry of the energy directors induces them to melt at a fast rate, and the resulting molten pads of plastic cool and harden thereby forming a strong weld.
Various shapes and patterns of energy directors have been used to create a bond between confronting surfaces. For example, the above referenced '359 Jakobsen patent discloses the use of energy directors shaped either as circles or as radially extending spokes for welding a base cup to a container. See FIGS. 10 and 11 of Jakobsen. U.S. Pat. No. 4,326,902 issued to Peddie discloses star-shaped, circular and cruciform energy directors for forming a weld between thermoplastic sheets. The use of a plurality of parallel ridge-shaped energy directors for welding together thermoplastic sheets is disclosed in U.S. Pat. No. 3,819,437 issued to Paine, U.S. Pat. No. 4,169,751 issued to Yen and U.S. Pat. No. 4,230,757 issued to Toner. U.S. Pat. No. 4,931,114 issued to Silva discloses the use of parallel ridge energy directors for welding a pompon streamer to a grip. The use of a plurality of concentric and interrupted circular energy directors to weld together an optical disc is disclosed by U.S. Pat. No. 4,564,932 issued to Lange. The use of a plurality of spike-shaped energy directors arranged in an annular array for welding together an optical disc is disclosed in U.S. Pat. No. 4,834,819 issued to Todo. Such a pattern is also disclosed in U.S. Pat. No. 5,403,415 issued to Schembri for welding a blood analysis circular rotor. An annular energy director is disclosed in U.S. Pat. No. 5,269,917 issued to Stankowski to weld together opposite halves of a filter housing.
Although various ones of the referenced energy director patterns may function satisfactorily for their intended purposes, there is a need for energy directors which maximize bonding strength between a plastic container and a separate plastic handle ultrasonically welded thereto. The bond should be sufficiently strong to permit lifting of a filled container having a capacity of one gallon or more. In addition, the container, the handle and the bond therebetween should be capable of withstanding the stresses and strains associated with hot-filling and handling of the container. Finally, the formation of the weld should be capable of being accomplished efficiently.